In fact the risks are very small; you're absolutely correct.
The question there that has been offered to me and to the society is that in our health system, imaging and diagnostic is usually done as a step to treatment. In this context, because the treatment is not immediately available...it would have to be repeated by the surgeon who would eventually do the treatment in the days before the treatment. While it obviously would answer the question of whether or not the blockage is present, because the treatments are not available, the diagnosis on its own, given that it would have to be repeated, is not easily available through the public health system.